A curious thing happened recently on Big Rock Mesa in Malibu. Home values on the steep hillside, devastated by a massive landslide six years ago, jumped dramatically. And that made the residents angry.

Under normal circumstances, which are rare on Big Rock, the residents would have been happy to see their homes reappraised by the county.

But, in this case, they suspect it is the county's way of justifying a tax increase of more than $100,000 apiece to pay for an elaborate pumping system that reduces the possibility of another major landslide.

Triple Assessment

Residents were stunned in June when the county revealed that it plans to triple the homeowners' tax assessment on Big Rock for the elaborate water drainage system. The county has rushed ahead with plans for the $13-million improvement package.

Then homeowners discovered that the county assessor's office was reappraising the hillside homes, raising the value of more than 200 homes by up to 80%. When they tried to find out why, they became infuriated at what they discovered.

State law limits the amount an agency can assess homeowners for an improvement project to 50% of the total value of the property in the assessment district. Since the appraised value of the homes in the district was $31 million, the assessments of nearly $26 million for the proposed drainage project and sewer system was far above the legal limit.

"We've been victimized again," said Big Rock resident Chuck Braverman. "On the one hand they're telling us the mountain is falling down and they need all this money to fix it, and on the other they're telling us that our houses are going way up in value. It's the ultimate bureaucratic Catch-22. It's unbelievable."

County officials deny there is any connection between the reappraisal and the proposed assessment district. The county assessor's office said that it reappraised 221 properties on Big Rock Mesa following a survey of home sales there during the first three months of the year.

Robert Knowles, spokesman for the assessor's office, said that recent home sale prices reflected a significant rise in value from the level that prevailed for several years after the 1983 landslide, which destroyed or damaged almost 250 homes. In fact, he said, his office was not even aware of the proposed assessment district to remove water from the hillside.

"It's a complete coincidence," he said. "I'm not aware of any connection between what we're doing and any improvement district. Our reasons for doing this have nothing to do with that."

However, suspicious Big Rock residents believe that the county is just trying to recoup some of the $35 million it is still shelling out as its part of the $97-million settlement for damages the homes suffered in the landslide.

The settlement grew out of a suit filed by the homeowners against the county and state for having approved development on Big Rock Mesa with seepage pits and horizontal drains rather than sewers. The county's action, they said, contributed to a rise in ground water that triggered the September, 1983, landslide on the mesa, a promontory that overlooks the ocean two miles west of Topanga Canyon.

'Pound of Flesh'

"This thing is Machiavellian in nature," said attorney Ken Chiate, who helped negotiate the settlement. "The county is getting its pound of flesh."

Residents, who believe that the proposed assessment district is far larger and more expensive than needed, said they plan to protest the planned tax increase and rise in home values. The prices for homes that were sold in Big Rock Mesa recently ranged from $75,000 to $675,000, and one homeowner who asked not to be named said the appraised value of his house jumped from $300,000 to $480,000.

More than 120 Big Rock homeowners met in Malibu Wednesday to plot strategy for a Sept. 14 hearing, when the plan will be presented to county supervisors. The Big Rock Improvement Committee, formed to monitor the county's pumping program, is trying to drum up support for a protest that would allow them to block the plan if more than 50% of the landowners in the district object to the proposal in writing.

Members of the group's steering committee said they would continue to negotiate with county public works officials to try to reduce the size and cost of the pumping program but added that they were not optimistic.

"We may survive the Big Rock landslide," said steering committee member Mike Caggiano, "but we may be buried under the assessments."